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Yr 3 > extracellular calcium homeostasis > Flashcards

extracellular calcium homeostasis Flashcards

1
Q

calcium and phosphate play a significant role in the formation of what

A

skeleton and teeth
regulation of biochemical pathways and signalling cascades

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2
Q

what are bones made out of

A

calcium phosphate

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3
Q

the homeostasis of plasma calcium is achieved by actions on three different hormones what are they

A

Metabolites of vitamin D
Parathyroid hormone
Calcitonin

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4
Q

what is the function of metabolites of vitamin D

A

increase calcium uptake

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5
Q

what is the role of the parathyroid hormone (calcium)

A

hypocalcaemia
acts on bones and increases resorption

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6
Q

What is the role of calcitonin

A

hypercalcaemia
wants to store calcium, moves Ca from extracellular space to be stored in the bone

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7
Q

where is the parathyroid hormone made

A

manufactured in chief cells of the parathyroid gland

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8
Q

heterozygous CaSR inactivating mutation in FHH means failure of what

A

inhibition of PTH secretion in high [Ca2+]e

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9
Q

during hypercalaemia calcium binds to what receptor
and causes what

A

GQ coupled receptors’
rise in intracellular Ca concentration -> inhibits exocytosis of PTH secretion

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10
Q

what three effects mediate numerous physiological effects

A

extracellular calcium homeostasis
nutrient sensor - parietal and G cells
enzyme secretion - alpha and beta cells

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11
Q

Where are PTH receptors expressed

A

osteoblasts in bone
proximal and distal tubules of kidneys

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12
Q

PTH is responsible for increasing

A

extracellular Ca2+

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13
Q

Bones - 1 degree primary effect
PTH stimulates _______ to recruit osteoblasts
Osteoblasts induce______

A

cytokines
osteoclasts

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14
Q

GI tract - ddegree - secondary effect
activates synthesis of 1,25-dihydroxyvitamin D and increases transcelllular uptake of Ca2+ from where

A

small intestine

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15
Q

Kidneys - 1 degree - primary effect
PTH increase ____ reabsorption by increasing activity of __________

A

Ca2+
Ca2+ channels and pumps

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16
Q

why is a thyroidectomy not fatal

A

there are small clusters of PTH producing cells outside of the parathyroid gland
trachea

17
Q

how is vitamin D converted to 1,25-dihyroxyvitamin D

A

hydroxylations

18
Q

secondary hydroxylations is regulated by

A

Growth hormone = ↑
Prolactin = ↑
Oestrogen = ↑
FGF23 = ↓
1, 25-Dihydroxyvitamin D = ↓

19
Q

what is the primary role of 1,25 dihydroxyvitamin D

A

contribute to homeostasis of calcium

20
Q

how does dihydroxyvitamin D contribute to homeostasis in the small intestine

A

increases calcium absorption

Diffuses into enterocytes and binds to vitamin D receptor (VDR) and increases gene expression
Increases calcium transport across the enterocyte membrane by increased expression of apical Ca2+ channels and basolateral Ca2+ transporters.

21
Q

how does dihydroxyvitamin D contribute to homeostasis in the kidneys

A

increases expression of Na+-Pi cotransporter
improves PTH-mediated Ca2+ reabsorption

22
Q

how does dihydroxyvitamin D contribute to homeostasis in the bone

A

increases number of osteoclasts

23
Q

where is calcitonin manufactured

A

clear cells of the thyroid gland

24
Q

what does calcitonin respond to

A

hypercalcaemia

25
Q

what is an antagonist action of PTH

A

calcitonin

26
Q

owhere in the bone are there calcitoonin receptors

A

osteoclasts

27
Q

how does calcitonin act on the bone

A

reduces rate of bone turnover, forcing release of Ca2+ in the bone

28
Q

testosterone maintains what in calcium homeostasis

A

bone density

29
Q

what do glucocorticoids do in calcium homeostasis

A

decrease maintenance and abundance of osteoblasts
but increase number and function of osteoclasts

30
Q

Fibroblast growth factor 23 (FGF23) is secreted by what

A

osteocytes

31
Q

Fibroblast growth factor 23 (FGF23) production is upregulated when

A

plasma concentrations rise

32
Q

Fibroblast growth factor 23 (FGF23) stimulates phosphate loss where

A

in the urine

33
Q

what is hypoparathyroidism

A

lack of PTH

34
Q

what is hyperparathyroidism

A

excess of PTH from parathyroid glands

35
Q

what is the primary cause of hyperparathyroidism

A

tumors

36
Q

what is a secondary cause of hyperparathyroidism

A

chronic kidney disease (lack of 1,25 - dihydroxyvitamin D
calcium malabsorption

Yr 3 (15 decks)

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